Inkjet printheads are devices for printing an image on a printing medium by ejecting droplets of ink onto a desired region of the printing medium. Depending on the mechanism of ejecting ink droplets, inkjet printheads may be classified into two different types: a thermal inkjet printhead; and a piezoelectric inkjet printhead. A thermal inkjet printhead requires ink to be heated to form ink bubbles and the expansive force of the bubbles causes ink droplets to be ejected, whereas a piezoelectric inkjet printhead requires a piezoelectric crystal to be deformed and the pressure due to the deformation of the piezoelectric crystal causes ink droplets to be ejected.
For a thermal inkjet printhead, the mechanism of ejecting ink droplets first involves heating the ink. When current in the form of a pulse wave is supplied to a heater, which may be in the form of a heating resistor, the ink surrounding the heater is quickly heated to about 300° C. Accordingly, the ink boils to generate bubbles, which expand to apply pressure to the ink filled in the ink chamber. Ultimately, the ink in the vicinity of a nozzle may be ejected through the nozzle in the form of droplets.
The thermal inkjet printhead may have a structure in which a chamber layer and a nozzle layer are sequentially stacked on a substrate on which a plurality of material layers are formed. A plurality of the ink chambers, which are filled with ink to be ejected, are formed in the chamber layer, and a plurality of nozzles through which ink may be ejected are formed in the nozzle layer. In addition, the structure includes an ink feed hole passing there through, which supplies ink to the ink chambers.